[FA-misc] Astro migration works, probably want to touchup the frontend but that can be in Phase 4

fictionarchive-web-astro/src/lib/auth/oidcConfig.ts

@@ -0,0 +1,35 @@
+import { UserManager, WebStorageStateStore, type UserManagerSettings } from 'oidc-client-ts';
+
+const authority = import.meta.env.PUBLIC_OIDC_AUTHORITY;
+const clientId = import.meta.env.PUBLIC_OIDC_CLIENT_ID;
+const redirectUri = import.meta.env.PUBLIC_OIDC_REDIRECT_URI;
+const postLogoutRedirectUri = import.meta.env.PUBLIC_OIDC_POST_LOGOUT_REDIRECT_URI ?? redirectUri;
+const scope = import.meta.env.PUBLIC_OIDC_SCOPE ?? 'openid profile email';
+
+export const isOidcConfigured =
+  Boolean(authority) && Boolean(clientId) && Boolean(redirectUri);
+
+function buildSettings(): UserManagerSettings | null {
+  if (!isOidcConfigured) return null;
+
+  return {
+    authority: authority!,
+    client_id: clientId!,
+    redirect_uri: redirectUri!,
+    post_logout_redirect_uri: postLogoutRedirectUri,
+    response_type: 'code',
+    scope,
+    loadUserInfo: true,
+    automaticSilentRenew: true,
+    userStore:
+      typeof window !== 'undefined'
+        ? new WebStorageStateStore({ store: window.localStorage })
+        : undefined,
+  };
+}
+
+export const userManager = (() => {
+  const settings = buildSettings();
+  if (!settings) return null;
+  return new UserManager(settings);
+})();